A novel single-layer unit cell structure is proposed to design a dual-band dual-linear-polarization reflectarray antenna with different beams for X and Ku bands. The unit cell structure is composed of a circular ring and two cross bow-tie structures combined by a circular patch. Five tunable geometric parameters can be optimized to achieve the required phase distributions of the reflectarray antenna with independent radiation patterns for each band which is a challenge for single-layer linearly polarized reflectarrays. Besides, the proposed unit cell structure has the ability to meet the demand of dual-polarization applications. A 301-element center-fed reflectarray with an octagon-shape aperture operating at X and Ku bands is designed, manufactured and measured to verify the dual-band performance of the proposed unit cell. The measured results show that the object of achieving different beams at different frequencies is realized with good radiation patterns at both designed frequencies. Besides, the similar radiation patterns for both linear polarizations are also achieved at both bands.
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